Efficient exosome separation utilizing dielectrophoretic force in conductive spiral microfluidic chips and validation via a reduced graphene oxide (rGO)-based biosensor

Uniformly sized exosomes were isolated using a conductive spiral microfluidic channel induced by hydrodynamics and dielectrophoretic (DEP) forces from a crude environment (a cell culture medium). The proposed channel was fabricated by mixing Ag flakes and polydimethylsiloxane, resulting in low resistances of 11.04 ± 2.87 Ω. This allowed the formation of a DEP force inside the channel by applying an external voltage. The DEP force captured small particles (such as exosomes) that were pushed to the corner by the Dean flow, significantly improving separation efficiency. The separation efficiencies of the hydrodynamic forces-induced microfluidic chip (HIMF) and the DEP force-assisted microfluidic chip (DAMF) were verified through the successful separation of 100 nm polystyrene beads (resembling exosomes in size) from 5 μm polystyrene beads (resembling cell size) as well as a mixture of purified exosomes and 5 μm polystyrene beads. Additionally, the detection signal of the separated exosomes using a reduced graphene oxide-based biosensor was confirmed as approximately four times higher than the signal of the supernatant before separation. Finally, the exosomes from lung adenocarcinoma cell H1437 were separated using the DAMF and compared with those isolated through ultrafiltration (UF). The exosomes separated by the DAMF exhibited a more consistent response across various concentrations than those isolated through UF, indicating that the DAMF had a minimal effect on the destruction of exosomes during the separation process. Consequently, our DAMF successfully separated exosomes from cell-containing media in one step, rendering the process remarkably simple with a high separation efficiency of 83%.